/**
* Constructs the shortest path array for the given graph.
*
* @param g input graph
* @param <V> a V object.
* @param <E> a E object.
*/
public FloydWarshall(Graph<V, E> g) {
int sz = g.vertexSet().size();
d = new double[sz][sz];
indices = new HashMap<V, Integer>();
// Initialise distance to infinity, or the neighbours weight, or 0 if
// same
for (V v1 : g.vertexSet()) {
for (V v2 : g.vertexSet()) {
if (v1 == v2) {
d[index(v1)][index(v2)] = 0;
} else {
E e = g.getEdge(v1, v2);
if (e == null) {
d[index(v1)][index(v2)] = Double.POSITIVE_INFINITY;
} else {
d[index(v1)][index(v2)] = g.getEdgeWeight(e);
}
}
}
}
// now iterate k times
for (int k = 0; k < sz; k++) {
for (V v1 : g.vertexSet()) {
for (V v2 : g.vertexSet()) {
d[index(v1)][index(v2)] =
Math.min(d[index(v1)][index(v2)], d[index(v1)][k] + d[k][index(v2)]);
if (Double.POSITIVE_INFINITY != d[index(v1)][index(v2)])
diameter = Math.max(diameter, d[index(v1)][index(v2)]);
}
}
}
}
/**
* @param graph the graph to be ordered
* @param orderByDegree should the vertices be ordered by their degree. This speeds up the VF2
* algorithm.
* @param cacheEdges if true, the class creates a adjacency matrix and two arrays for incoming and
* outgoing edges for fast access.
*/
public GraphOrdering(Graph<V, E> graph, boolean orderByDegree, boolean cacheEdges) {
this.graph = graph;
this.cacheEdges = cacheEdges;
List<V> vertexSet = new ArrayList<>(graph.vertexSet());
if (orderByDegree) {
java.util.Collections.sort(vertexSet, new GeneralVertexDegreeComparator<>(graph));
}
vertexCount = vertexSet.size();
mapVertexToOrder = new HashMap<>();
mapOrderToVertex = new ArrayList<>(vertexCount);
if (cacheEdges) {
outgoingEdges = new int[vertexCount][];
incomingEdges = new int[vertexCount][];
adjMatrix = new Boolean[vertexCount][vertexCount];
}
Integer i = 0;
for (V vertex : vertexSet) {
mapVertexToOrder.put(vertex, i++);
mapOrderToVertex.add(vertex);
}
}
/**
* Creates a new iterator for the specified graph. Iteration will start at the specified start
* vertex. If the specified start vertex is <code>
* null</code>, Iteration will start at an arbitrary graph vertex.
*
* @param g the graph to be iterated.
* @param startVertex the vertex iteration to be started.
* @throws IllegalArgumentException if <code>g==null</code> or does not contain <code>startVertex
* </code>
*/
public CrossComponentIterator(Graph<V, E> g, V startVertex) {
super();
if (g == null) {
throw new IllegalArgumentException("graph must not be null");
}
graph = g;
specifics = createGraphSpecifics(g);
vertexIterator = g.vertexSet().iterator();
setCrossComponentTraversal(startVertex == null);
reusableEdgeEvent = new FlyweightEdgeEvent<V, E>(this, null);
reusableVertexEvent = new FlyweightVertexEvent<V>(this, null);
if (startVertex == null) {
// pick a start vertex if graph not empty
if (vertexIterator.hasNext()) {
this.startVertex = vertexIterator.next();
} else {
this.startVertex = null;
}
} else if (g.containsVertex(startVertex)) {
this.startVertex = startVertex;
} else {
throw new IllegalArgumentException("graph must contain the start vertex");
}
}
/** {@inheritDoc} */
public void generateGraph(
Graph<V, E> target, VertexFactory<V> vertexFactory, Map<String, V> resultMap) {
if (size < 1) {
return;
}
// Add all the vertices to the set
for (int i = 0; i < size; i++) {
V newVertex = vertexFactory.createVertex();
target.addVertex(newVertex);
}
/*
* We want two iterators over the vertex set, one fast and one slow.
* The slow one will move through the set once. For each vertex,
* the fast iterator moves through the set, adding an edge to all
* vertices we haven't connected to yet.
*
* If we have an undirected graph, the second addEdge call will return
* nothing; it will not add a second edge.
*/
Iterator<V> slowI = target.vertexSet().iterator();
Iterator<V> fastI;
while (slowI.hasNext()) { // While there are more vertices in the set
V latestVertex = slowI.next();
fastI = target.vertexSet().iterator();
// Jump to the first vertex *past* latestVertex
while (fastI.next() != latestVertex) {;
}
// And, add edges to all remaining vertices
V temp;
while (fastI.hasNext()) {
temp = fastI.next();
target.addEdge(latestVertex, temp);
target.addEdge(temp, latestVertex);
}
}
}
/**
* Creates a new labels graph according to the regular graph. After its creation they will no
* longer be linked, thus changes to one will not affect the other.
*
* @param regularGraph
*/
public GraphOrdering(Graph<V, E> regularGraph) {
this(regularGraph, regularGraph.vertexSet(), regularGraph.edgeSet());
}
public FloydWarshallShortestPaths(Graph<V, E> graph) {
this.graph = graph;
this.vertices = new ArrayList<V>(graph.vertexSet());
}
/**
* Creates an object to calculate shortest paths between the start vertex and others vertices
* using the Bellman-Ford algorithm.
*
* @param graph
* @param startVertex
*/
public BellmanFordShortestPath(Graph<V, E> graph, V startVertex) {
this(graph, startVertex, graph.vertexSet().size() - 1);
}